Paleontologists often suffer from limited access to prime reference materials for taxonomic studies because the necessary materials are unique and rare. Frequent handling is discouraged to minimize the risk of damage or loss. In such situations, the researcher needs to consult literature and atlases where the specimens are described and illustrated. In traditional taxonomic monographs specimens are presented in two-dimensional (2D) photographs, usually in front view, side view, and back view, often with additional enlargements to illustrate morphological details. In some cases it may be advantageous if the structures could be shown in three dimensions (3D) or as an animation to better understand the anatomy of a shell. Of course, sophisticated imaging techniques such as scanning of the topography with a laser beam, X-ray computer tomography, or photogrammetric methods have been developed. In recent years these once esoteric computer reconstruction techniques have become more available, most of them for macroscopic applications. Examples can be found in disciplines from medical surgery to paleoanthropology and in paleontology (Sutton et al. 2001; Zollikofer et al. 1998; Zollikofer and Ponce de Léon 2000, Ponce de Léon and Zollikofer 2001). Impressive examples for Neanderthal skull reconstructions, for example, can be found at the Anthropological Institute of the University of Zürich Computer-assisted Paleonanthropolgy and the Neanderthals. For microscopic applications, however, these techniques are limited. Lyons and Head (1998) presented a 3D visualization technique, that can be applied to scanning electron photomicrographs. For light microscopy, a similar approach is complicated by limited depth of field, which causes unsharp regions to appear in the images.
This latter problem is addressed in the present report. A method is presented herein to illustrate microscopic objects in the 100 µm to 1000 µm size range under reflected light in 3D stereo view, at extended depth of focus. In addition, collections of such images can be animated, so that the object can be observed from all sides on a computer monitor. Planktonic foraminifers (marine pelagic, calcite shell-secreting protists) were used to illustrate the technique, but the method can easily be applied to other microfossils (e.g., radiolarians, benthic and larger foraminifera, ostracods).
The method was developed using a Leica binocular microscope mounted on a AX microscope carrier. The up-and-down movement of the objective during focusing was measured with an electronic precision caliper. Stereo-pair images were taken at a series of subsequent focal planes with a digital video camera. Applying this technique to a series of images from varying positions, and using commercial virtual reality software allowed generation of an animation for 3D stereographic view of the microfossil at extended focal resolution.
This technique is ideal to illustrate unique type specimens in three dimensions. The method may also be used to construct digital taxonomic atlases or illustrated micropaleontological databases. Another obvious application involves the preparation of computer animations of microfossils for teaching purposes or oral presentations, animations in public displays, and exhibition of microfossils in museums.